1. Field of the Invention
The present invention relates generally to x-ray systems, devices, and related components. More particularly, exemplary embodiments of the invention concern a high voltage cable assembly configured to facilitate a reduction in arcing and related problems when the high voltage cable is mated with a corresponding receptacle.
2. Related Technology
The various components employed in x-ray tubes and other high temperature, high-voltage applications are typically required to operate consistently and reliably under extreme conditions for sustained periods of time. In the case of an x-ray device for example, the generation of x-rays, which generally involves accelerating electrons at high speed to a target surface on an anode, can result in operating temperatures as high as 1300° C.
Not only are such components routinely exposed to high operating temperatures, but such components are often subjected to extreme thermal cycles as well. For example, x-ray devices are typically reach a required operating temperature within a time span of just a few minutes. Thus, the rate of change of temperature with respect to time is relatively high. The thermal stresses imposed by such steep temperature gradients often have various destructive or detrimental effects on the structure and performance of the components of the device.
One area where such thermal effects are of particular concern relates to high voltage cables and associated devices and equipment that are employed in connection with high voltage equipment such as x-ray devices. Typical high voltage cables include a cable having one or more electrical conductors electrically isolated from each other and wrapped in a protective covering or sheath. Examples of such cables include the so-called R3, R5, R12 and R24 cables.
Typically, a terminal attached to the end of the cable includes a conical rubber element that terminates, at the narrow end of the cone, in a pair of electrical contacts, each of which is connected with a corresponding electrical conductor of the cable. In general, the conical rubber element is configured and arranged to be received within a correspondingly shaped receptacle so that the contacts on the terminal come into contact with corresponding contacts positioned near the bottom of the receptacle when the conical rubber element is fully received within the receptacle. In many cases, the high voltage cable also includes threads, a flange, or other type of connector to enable the high voltage cable to be removably attached to the receptacle.
Many of such high voltage cable assemblies are configured such that when the cable is operably attached to the receptacle, the joint between the rubber terminal and the cable is located outside of the receptacle. Such arrangements were initially employed in relatively lower temperature applications and proved useful in at least some of those applications. Problems have arisen however where attempts have been made to use such high voltage cable assemblies in applications that were not intended or anticipated.
At least some of the problems experienced in connection with the use of typical cable assemblies in high voltage, high temperature operating environments concern the effects of the associated thermal conditions on the rubber terminal element of the terminal of the cable assembly. In particular, heating of the rubber element causes the portion of the rubber element located outside the receptacle to expand, or spill, over the top of the receptacle so that an annular ring or bulge is formed on top of, and outside, the receptacle. This effect commonly occurs at or near the recommended maximum operating temperature of the cable assembly.
As the cable assembly cools and contracts, the ring contracts partially, but not to the extent that the rubber element reassumes its original configuration. As a result, an annular ring remains fixed in position outside the receptacle. As discussed below, this situation is problematic.
In particular, the position of the annular ring outside the receptacle prevents the terminal of the cable assembly from retracting to the initial, fully seated, position within the receptacle. Consequently, the contacts at the end of the terminal are no longer in physical contact with the corresponding contacts of the receptacle. Thus, when the device is reenergized, the physical separation between the contacts of the terminal and the contacts of the receptacle, in connection with the associated high potential, often causes arcing between the cable assembly and the receptacle, as well as related problems and conditions. Such arcing can damage, or destroy, the cable assembly and/or the device to which the cable assembly is mated.
A related effect is that, because the annular ring, or bulge, remains fixed in position outside the receptacle, the main body of the conical rubber element, located inside the receptacle, tends to pull away from the interior of the receptacle as the cable assembly cools. This separation creates an air gap that causes arcing and related problems when the device is reenergized.
In view of the foregoing, and other, problems in the art, it would be useful to provide a cable assembly configured to reduce, or eliminate, the likelihood of occurrence of arcing and related problems and conditions due to uncontrolled deformation of the terminal element of the terminal.